Column: Oregon beats Arizona for Pac-12 title like Duck, Duck, whoosh!

Oregon committed 11 first-half penalties and quarterback Marcus Mariota was definitely off his game.

The players belonging to the team many thought was national championship-ready sulked into the locker room looking for a dry place to hide.

The odd part was Oregon led, 23-0.

Maybe the bad news was also the good news.

Oregon ended up defeating Arizona, 51-13, to win the Pac-12 championship everyone said, from Media Day on, was Oregon’s to lose.

If the Ducks could play sloppily and still win big, imagine the possibilities if they clean up the silly mistakes by New Year’s Day.

Oregon (12-1) completed the hard, first leg of the journey on a rainy Friday night, before an announced crowd of 45,618 at Levi’s Stadium.

Friday’s win clinched the first spot in this year’s four-team playoff.

“This is a huge accomplishment for us,” Mariota said. “Now we need to continue to improve and get better to get ready for whoever comes next.”

No matter what happens in the Saturday matchups, Oregon probably is headed to a Jan. 1 semifinal game at the Rose Bowl.

Oregon is No. 2 in the latest College Football Playoff ranking and will either go to Pasadena as the second-seeded team, or as No. 1 if Missouri upsets No. 1 Alabama in the Southeastern Conference title game.

The playoff teams will be announced Sunday.

Mariota also very likely, with his performance, clinched this year’s Heisman Trophy. He would become only the second player from the Pacific Northwest to win the award. Oregon State quarterback Terry Baker won in 1962.

The general thinking was Mariota could lose the trophy only with a poor performance in a loss.

It looked sketchy early as Oregon drove to the Arizona 16-, 10- and 25-yard lines but came away with only two field goals.

Mariota overthrew some passes and looked tentative at times against the Arizona team that has defeated Oregon the last two seasons.

He finally loosened up a sloppy, dull, 6-0 game with a seven-yard scoring run with 7:27 left in the half.

Mariota might have sealed the Heisman later in the half, when he rescued the Ducks from a third-and-16 hole with a 73-yard pass and run to Charles Nelson.

Mariota capped the drive with a four-yard run.

Oregon found its groove in the second half and proceeded to empty out a half-empty stadium.

The Ducks head to the playoff with considerable momentum, having won eight consecutive games by 24 points or more.

Oregon’s offense ended up scoring 51 points, but the story of the game was a defense that could be rounding into national championship form.

Oregon has given up 19 or fewer points in four of its last five games.

The Ducks pitched a first-half shutout against Arizona and held the Wildcats to 25 yards on 25 plays.

Mariota buffed up his Heisman case with two second-half scoring passes and another short rushing touchdown. He finished the night completing 25 of 38 passes for 303 yards and rushing for 33 yards and three touchdowns.

He finished the regular season with 53 total touchdowns — 38 passing, 14 rushing and one receiving.

Case closed?

“If this guy isn’t what the Heisman Trophy is all about, I’m in the wrong profession,” Oregon Coach Mark Helfrich said.

Arizona, which had a chance to make the playoff with a win, instead froze in the headlights. Quarterback Anu Solomon completed six of 12 passes for 34 yards before being pulled.

“Wasn’t a good night,” Arizona Coach Rich Rodriguez said. “They played well, we didn’t.”

Oregon outgained Arizona, 617 yards to 224.

The lopsided defeat might have cost Arizona (10-3) a chance to play in the Fiesta Bowl.

The Pac-12, though, should thank the moon and the stars for the new four-team playoff.

The league had a hard time catching a cold in the 16-year history of the Bowl Championship Series, watching most title games from the sidelines.

If the BCS was still in place, in fact, Oregon would now have to pray for Georgia Tech to upset Florida State on Saturday.

Simulations of the old system, which used polls and computers to choose two teams, are still being run on various websites. They have Alabama and Florida State in first and second, with Oregon a distant third.

It’s still going to take two more wins to claim the league’s first title since USC’s vacated crown of 2004.

Yet, while it was a rainy, sloppy day in the Pac-12, it was also a new day.

chris.dufresne@latimes.com